From 1a67acf443d4b107ef486daf88dbfe6f89959453 Mon Sep 17 00:00:00 2001
From: ak <alok@harmony.one>
Date: Sun, 26 Aug 2018 23:34:26 -0700
Subject: [PATCH] wip pow

---
 waitnode/pow.txt | 82 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 82 insertions(+)
 create mode 100644 waitnode/pow.txt

diff --git a/waitnode/pow.txt b/waitnode/pow.txt
new file mode 100644
index 000000000..e1ae54168
--- /dev/null
+++ b/waitnode/pow.txt
@@ -0,0 +1,82 @@
+package waitnode
+
+import (
+	"bytes"
+	"crypto/sha256"
+	"fmt"
+	"math"
+	"math/big"
+)
+
+var (
+	maxNonce = math.MaxInt64
+)
+
+const targetBits = 24
+
+// ProofOfWork represents a proof-of-work
+type ProofOfWork struct {
+	Challenge int32
+	target    *big.Int
+}
+
+// NewProofOfWork builds and returns a ProofOfWork
+func NewProofOfWork(c int32) *ProofOfWork {
+	target := big.NewInt(1)
+	target.Lsh(target, uint(256-targetBits))
+
+	pow := &ProofOfWork{c, target}
+
+	return pow
+}
+
+func (pow *ProofOfWork) prepareData(nonce int) []byte {
+	data := bytes.Join(
+		[][]byte{
+			pow.Challenge.,
+			IntToHex(int64(targetBits)),
+			IntToHex(int64(nonce)),
+		},
+		[]byte{},
+	)
+
+	return data
+}
+
+// Run performs a proof-of-work
+func (pow *ProofOfWork) Run() (int, []byte) {
+	var hashInt big.Int
+	var hash [32]byte
+	nonce := 0
+
+	fmt.Printf("Mining the block containing \"%s\"\n", pow.block.Data)
+	for nonce < maxNonce {
+		data := pow.prepareData(nonce)
+
+		hash = sha256.Sum256(data)
+		fmt.Printf("\r%x", hash)
+		hashInt.SetBytes(hash[:])
+
+		if hashInt.Cmp(pow.target) == -1 {
+			break
+		} else {
+			nonce++
+		}
+	}
+	fmt.Print("\n\n")
+
+	return nonce, hash[:]
+}
+
+// Validate validates block's PoW
+func (pow *ProofOfWork) Validate() bool {
+	var hashInt big.Int
+
+	data := pow.prepareData(pow.challenge.Nonce)
+	hash := sha256.Sum256(data)
+	hashInt.SetBytes(hash[:])
+
+	isValid := hashInt.Cmp(pow.target) == -1
+
+	return isValid
+}